Hemispherical resonator gyroscopes (HRG) have superior performance, however, the cost for macromachining a high-performance HRG is high. Sagem Defense Securite proposed the use of an electrode for measuring an axial motion, resulting in a small size and a relatively easy assembly process. To further reduce the cost and the size, researchers have started to focus on the miniaturization of a shell resonator gyroscope, and especially HRG. As a kernel of an MEMS shell resonator gyroscope, a micro shell resonator device determines the performance of the micro shell resonator gyroscope. The shell resonator gyroscope is a high-performance gyroscope among Coriolis vibratory gyroscopes. Limited by features and development of MEMS technology, the development of micro shell resonator gyroscope is slow. The MEMS technology features a silicon-based surface process, and high costs and low accuracy of three-dimensional MEMS technology. Due to fabrication restrictions, success in fabrication of high-performance shell resonator gyros made from a micro hemispherical resonator or a micro cylindrical resonator has not yet achieved. Compared with these two kinds of shell resonator gyroscopes, a micro-ring vibratory gyroscope is being more widely researched.
The key to implement a high-performance micro shell resonator gyroscope is fabrication of a high-performance micro shell resonator device, which is embodied in three aspects: fabrication of a high-performance micro shell resonator, fabrication and assembly of electrodes, and vacuum packaging. The micro shell resonator directly determines the performance of the device. The fabrication of the electrodes has the following two situations. In the first situation, the electrodes and the resonator are integrally fabricated and formed; and in the second situation, the electrodes are independently fabricated and then are assembled with the resonator. The key of the assembly lies in that the intervals between the electrodes and the resonator need to keep consistent, as well as their areas, thus maintaining capacitances of the electrodes and the resonator to be consistent. The high-performance micro shell resonator gyroscope needs to operate in a high vacuum environment, and therefore the vacuum packaging becomes a crucial step in design and fabrication. However, vacuum packaging using the MEMS technology has low vacuum degree. Therefore, the interval between the electrode and the resonator needs to be appropriately increased in design in consideration of air damping. All the considerations aim at achieving a high-performance micro shell resonator device. Two of the performance indexes are most important: symmetry (specifically indicated by AO and energy loss (specifically indicated by a Q value).